I agree with everyone else, definately be yourself. You can usually figure out when someone isnt

Relax and stay cool and just smile like your having a good day, after all these girls were all in your shoes at one point. They are no different then you are. I always think it helps to go in thinking positive, but to never have high expectations. Another thing you notice with alot of girl is that they dont speak up, but sit smile and nod..... NEVER be afraid to speak in a convo or initiate one
Have a good time!